A motorboat takes 18 hours to go downstream, and it takes 36 hours to return the same distance. Find the ratio of the speed of the boat in still water to the speed of the stream.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 3 : 1.
Let the speed of boat in still water be x km/h and speed of stream be y km/h.
Downstream speed = (x + y) km/h
Upstream speed = (x - y) km/h
(x + y) × 18 = (x - y) × 36
⇒ x + y = 2x - 2y
⇒ x = 3y
⇒ x : y = 3 : 1